Electrosurgical instruments are commonly used for the cutting/vaporisation and/or desiccation/coagulation of tissue in surgical intervention, most commonly in “keyhole” or minimally invasive surgery. The terms “cutting” and “vaporization” relate to the removal of tissue, whether by resection or by the volumetric removal of tissue. Similarly, the terms “desiccation” and “coagulation” relate to the creation of lesions in tissue, the necrosis of tissue, and to the prevention of bleeding.
Endoscopic instruments are often used in gastroenterology or cardiac surgery, and such instruments are normally introduced through a lumen within the patient's body. These instruments are therefore of a relatively small size, often no more than 5 mm in diameter. They are deployed at the end of a relatively long flexible shaft, such that they can be manoeuvred within a lumen as described above.
One instrument of this type is described in U.S. Pat. No. 7,648,501. It includes a cutting electrode deployable from the end of a catheter, and coagulation electrodes present on the instrument tip surrounding the cutting electrode. The present invention attempts to provide an improvement to endoscopic instruments of this type.